Explain
how chemical formulas can be used to describe elements and molecules.

Identify
the chemical formulas for several common substances.

What
are chemical formulas and how are they used?

In order to make it easier to describe
elements and molecules, chemical formulas are used. For example,
H represents one atom of hydrogen and "O" represents
one atom of oxygen. If we want to represent two atoms of hydrogen,
instead of writing H H, we write H2.
The subscript "2" means that two atoms of the element
hydrogen have joined together to form a molecule. A subscript
is only used when more than one atom is being represented. The
graphic below illustrates the formula for water using symbols.

Some more common molecules
and their chemical formula.

Carbon Dioxide >
CO2

Ammonia > NH3

Sugar > C6H12O6

Rubbing Alcohol > C3H7OH

Review:

Chemical
formulas are used to describe the types of atoms and their numbers
in an element or compound.

The atoms
of each element are represented by one or two different letters.

When more
than one atom of a specific element is found in a molecule,
a subscript is used to indicate this in the chemical formula.